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Article Dans Une Revue The Astrophysical Journal Année : 2022

Trends in Silicates in the β Pictoris Disk

Cicero X. Lu
  • Fonction : Auteur
B. A. Sargent
Dan M. Watson
  • Fonction : Auteur
Joel D. Green
  • Fonction : Auteur
G. C. Sloan
Isabel Rebollido
Michael W. Werner
  • Fonction : Auteur
Winston Wu
Kadin Worthen
Cicero Lu
Christine Chen
Dan Watson
Joel Green
Michael Sitko
Dean Hines
Julien Girard
Michael Werner
Karl Stapelfeldt

Résumé

Abstract While β Pic is known to host silicates in ring-like structures, whether the properties of these silicate dust vary with stellocentric distance remains an open question. We re-analyze the β Pictoris debris disk spectrum from the Spitzer Infrared Spectrograph (IRS) and a new Infrared Telescope Facility Spectrograph and Imager spectrum to investigate trends in Fe/Mg ratio, shape, and crystallinity in grains as a function of wavelength, a proxy for stellocentric distance. By analyzing a re-calibrated and re-extracted spectrum, we identify a new 18 μ m forsterite emission feature and recover a 23 μ m forsterite emission feature with a substantially larger line-to-continuum ratio than previously reported. We find that these prominent spectral features are primarily produced by small submicron-sized grains, which are continuously generated and replenished from planetesimal collisions in the disk and can elucidate their parent bodies’ composition. We discover three trends about these small grains: as stellocentric distance increases, (1) small silicate grains become more crystalline (less amorphous), (2) they become more irregular in shape, and (3) for crystalline silicate grains, the Fe/Mg ratio decreases. Applying these trends to β Pic’s planetary architecture, we find that the dust population exterior to the orbits of β Pic b and c differs substantially in crystallinity and shape. We also find a tentative 3–5 μ m dust excess due to spatially unresolved hot dust emission close to the star. From our findings, we infer that the surfaces of large planetesimals are more Fe-rich and collisionally processed closer to the star but more Fe-poor and primordial farther from the star.
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hal-03862674 , version 1 (21-03-2023)

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Cicero X. Lu, Christine H. Chen, B. A. Sargent, Dan M. Watson, Carey M. Lisse, et al.. Trends in Silicates in the β Pictoris Disk. The Astrophysical Journal, 2022, 933 (1), pp.54. ⟨10.3847/1538-4357/ac70d1⟩. ⟨hal-03862674⟩
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